The present invention relates to a composition and a process for reducing the adhesion of expandable polystyrene beads to one another. The production of expandable polystyrene (EPS) involves suspension of polystyrene beads in a stirred reactor. A blowing agent such as pentane, is introduced into the reactor for impregnation of the polystyrene beads. After a suitable time for impregnation, the polystyrene beads are removed from the reactor, dried and partially expanded to form a pre-puff by subjecting the beads to steam in an unconfined space. After sufficient aging, the pre-puffs are then placed in the desired mold and subjected to steam for expansion of the pre-puff into the final desired form within the confines of the mold. It has been found, however, that polystyrene beads impregnated with a blowing agent have a tendency to adhere to one another during pre-expansion, a characteristic known as "clumping". Clumping, most prevalent in the pre-expander where the pre-puffs are formed from beads, causes the pre-expander to become clogged.
Common anti-clumping agents include silicon dioxide, calcium silicate, magnesium carbonate, and zinc stearate/calcium silicate.
It would be desirable, therefore, to obtain a composition and a process which not only reduces or eliminates the clumping tendencies of expandable polystyrene, but which also is compatible with the expanded polystyrene product.